Centrifugally actuated control



y 5, 5 B. L. BRUCKEN ETAL 3,131,566

CENTRIFUGALLY ACTUATED CONTROL Original Filed June 27, 1958 sShets-Sheet 1 INVENTORS Byron L. Bracken BY rho/770$ The/r Af/omey B.BRUCKEN ETAL 3,131,566 CENTRIFUGALLY ACTUATED CONTROL May 5, 1964 3Sheets-Sheet 2 Original Filed June 27, 1958 INVENTORS 0 8 M. n I 5 0 mmW0 5m w The/r Attorney y 5, 1964 B. BRUCKEN ETAL 3,131,566

CENTRIFUGALLY ACTUATED CONTROL 3 Sheets-Sheet 3 Original Filed June 27,1958 High Speed Running Condition .Srorf Winding Curouf for born Highand Low Speed Current in Amperes United States Patent CENTRIFUGALLYACTUATED CONTROL Byron L. Bracken, Dayton, and Thomas H. Fogt, WestCarrollton, Ohio, assignors to General Motors Corporation, Detroit,Mich, a corporation of Delaware Original application June 27, 1958, Ser.No. 745,152. Divided and this application Oct. 22, 1962, Ser. No.231,993 3 Claims. (Cl. 73--537) This is a division of our copendingapplication Serial No. 745,152, filed June 27, 1958, and relates to acontrol circuit for multi-speed motors and more particularly to acentrifugally actuated control circuit for use with multi-speed washingmachines.

With the advane of man-made fabrics, the washing machine art has foundit necessary to revise washing procedures to make them adaptable to thenew fabrics. For this purpose, the washing machines in current vogueinclude a drive mechanism capable of agitating the clothes at two ormore speeds. Furthermore, such mechanism is arranged to spin the clothesin a centrifuging operation at two or more speeds to remove the waterfrom the clothes. It should be apparent that variable .loads are imposedon and variable speeds are required of any motor utilized in suchdrivemechanisrn. During the spin cycle, for instance, a considerabletorque is required to initiate the rotation of a laundry tub up to aspeed where the water is substantially spun from the tub. As the Wateris removed and the tub reaches a maximum spinning speed, the torquerequired is much less. An-

other situation requiring a degree of motor flexibility arises in casesof blockage within the tub tending to stall the motor during either theagitating action or the spinning action. It is desirable, therefore, toselect a motor which will meet these conditions automatically withoutrequiring complicated sensing devices for the various load situationsand without requiring the addition of motor control switches to thealready complicated washing machine timer. A multi-speed induction motorhas the desired operating characteristics to satisfy these loadrequirements when circuited in accordance with this invention.

A multi-speed motor in which the torque varies inversely as the speedhas been found applicable. These motors are capable of being operated ata number of different speeds and adapted for greatest torque at lowspeed.

A specific object of this invention is to increase a start windingsoperational range for two-speed motor application by modifying acentrifugally actuated control device whereby said device is effectiveto deenergize the start winding above low speed and below high speed andto reenergize the start winding below low speed.

Another object of this invention is to provide a twospeed, single startwinding motor with a manually operable speed selector switch and acentrifugally actuated switch for cutting out the start winding uponmotor acceleration and establishing the circuitry necessary for thespeed selected, said centrifugally actuated switch being restrained byspring biased tangs upon motor deceleration to prevent the switch fromreenergizing the start winding. 7 q i It is also an object of thisinvention to provide a single weight centrifugal switch with means foraltering the speed at which the switch is actuated.

- Further objects and advantages of the present invention will beapparent from the. following description, reference being had to theaccompanying drawings where- 'in a preferred embodiment of the presentinvention is clearly shown.

In the drawings:

FIGURE 1 is an elevational view of a washing ma chine, with parts brokenaway, equipped with a multispeed motor for reciprocating an agitator andspinning a tub;

FIGURE 2 is a schematic wiring diagram including a 48 pole consequentpole motor, a manually operable speed selector switch had acentrifugally actuated control switch;

FIGURE 3 is a fragmentary sectional view of a deenergized two-speedelectric motor provided with the centrifugal speed switching means ofthis invention;

FIGURE 4 is an elevational view taken along line 4-4 of FIGURE 3 showingthe centrifugal weight delay spring;

FIGURE 5 is a diagrammatic view of the centrifugal switch and itsactuating weight immediately after motor energization with start windingcontacts engaged;

FIGURE 6 is a diagrammatic view of the centrifugal switch and itsactuating weight in motor accelerating position;

FIGURE 7 is a diagrammatic View of the centrifugal switch and actuatingweight during high speed motor running position;

FIGURE 8 is a diagrammatic view of the centrifugal switch and actuatingweight during low speed motor running position; and

FIGURE 9 is a graph showing typical operating characteristics of a 6 HR,volts, 60-cycle, two-speed motor acceptable for use in multi-speedWashing machines and suitable for use with this invention.

In accordance with this invention, a washing machine 10 having anagitator 12 and a tub 14 is provided with a multiple speed motor 16. Themotor 16, by means of an agitating and spinning mechanism 18 such as istaught in Sisson 2,758,685, issued August 14, 1956, is adapted to causethe agitator 12 to agitate at two or more speeds and the laundry tub 14to spin at two or more speeds. A conventional belt drive 20 may beutilized in transmitting the rotative power of motor 16 to the agitatingand spinning mechanism 18. Again, in accordance with conventionalpractice, water may be supplied to the laundry tub 14 through athermostatic valve arrangement 22. To facilitate selective control ofthe washing machine operation, the machine may include a timer control24 and a speed selector 26.

With this arrangement of washing machine components the operator mayplace a load of clothes to be washed within the laundry tub 14 throughan access opening (not shown) in the top of the machine 10. The timer 24may be set to initiate a washing cycle and the speed selector 26 set foreither high or low operating speed. If low speed is selected, forinstance, the agitator 12 will agitate for a period controlled by thetimer 24. At the conclusion of this agitating or washing action, thetimer 24 will condition the motor circuit to initiate a removal of thesoiled washing water Within the tub 14. This is accomplished by spinningthe tub in a manner to cause the water to flow through the openings 23in the laundry tub 14 into a collecting chamber 30 disposed below. Fromthe chamber 30 a pump 32 may be utilized to remove the water to a remotedrain location by means of any suitable conduit 34. Fresh rinse Watermay then be supplied to the tub 14 through the valve 22 and a secondagitation or rinse cycle initiated by the timer 24. Following this, therinse water is removed from the tub 14 with another spinning operationof the tub. Since low speed has been selected, both the agitation andthe spinning action are accomplished at the low speed of motor 16.Durnig the spinning of tub 14, a variable load is placed on the motor16, viz. with the tub 14 full of water, a greater resistance to rotationis imposed upon the motor 16 and the motor rotates more slowly at thebeginning of the spincycle. It is these variations from the synchronousmotor speeds that are sensed centrifugally by the concepts of thisinvention to control the motor to meet the changing load'conditions.

This invention particularly concerns the operation or control of awashing machine mechanism to operate in any combination of two washspeeds and two spin speeds. The drive is through a reversible motor thatcauses the mechanism to pulse in one direction and to spin in theopposite direction. The motor is a consequent pole (4-8 pole) motor thatoperates at 1,725 or 850 r.p.m. Speed selection is accomplished byconnecting two sections of the motor main winding in parallel for highspeed and in series for low speed. Furthermore, this motor controlconcept contemplates the use of only one phase or start winding in themotor, which is thus started always in high speed. The utility of thiscontrol and motor circuit lies in the fact that acceleration of themotor is accomplished in a salient pole arrangement where the motortorque is high and continuous speed is reached in the consequent polearrangement, if selected, at lower speeds where there is much lesstorque available, and, in fact, little required in washing machineapplication. The unique and novel feature of this control circuit isbased on the fact that when motor torque is needed, the motor remains orreverts to the high speed, high torque circuit arrangementa situationoccurring (1) during start, (2) during excessive overload, or (3) stallconditions. 7

With reference to FIGURE 2, the motor control concepts of this inventionare shown in a circuit for a motor 16 of the consequent pole type. Themotor is wound with a first main winding 36 and a second main winding38. A start winding 40 is included in an internal motor circuit with acapacitor 42. Extending from the motor casing is a first lead 44, a'secondfio'r center tap lead 46 and a third lead 48, and from the startwinding circuit leads 50 and 52. A speedselector switch, shown generallyat 54, is designed for high and low speed motor settings. Tocentrifugally sense the washing machine load conditions imposed uponmotor 16, a centrifugal switch 56 is included in the circuit. The timer24 is utilized to energize the. motor circuit through a cam actuated.timer switch 58 at any time that motor operation is desired during awashing machine cycle. The timer 24 includes also motor reversingswitches 60, 61 adapted to close agitating contacts 62 during anypulsation portion of the wash cycle, and contacte 64 during anycentrifuging or tub spinning portion of the washing cycle. I

The centrifugal switching 'means 56 iscomprised of a control board 66 ofnonconducting material, and a rockably mounted skillet or switch portion68; The control board 66 has fixed thereto skillet support pins lit, 72which act to retain the skillet in correct relationship to V the board66. As suggested by the dashed'lines in FIG URE 2, the control circuitlines are attached to connecting pieces on the back of the control board66 which extends through the board into selective engagement withcontacts carried on the rocking skillet 68. To eliminate short circuitarc-over in a manner to be described more fully hereinafter, the controlboard 66 has an extended portion 1'74 at one'side thereof which isadapted to carry a" fixed 78 is attached. Further contact 76 to which acircuit line 4. engaged from the control board 66. Insulating bushings92 circumscribe the skillet apertures 84, 86 to insulate the pins 70, 72at the point where they pass through the skillet. Motor running contacts94, 96 are carried on the control board and arranged to mate withskillet motor running contacts 8, 180. It will be noted that contact 94is not connected to any line in the circuit, its only function being tobalance the skillet 68 when in centrifugally actuated position. Carriedalso on the skillets control board 66 are start winding contacts 162,104 arranged to mate respectiveiy with skillet start winding contacts106, 108. Contacts 98, 100 are carried by the straight or flat skilletportion 82 but are insulated therefrom by insulating bushings 110. Onthe other hand, start winding skillet contacts 106, 168 are carrieddirectly on the skillet portion 82. A bridging member 112 connectscontacts 98, 100 and is insulated also from skillet 68. Connected alsoto skillet contact 98 and bridging member 112 is an arm 114,

details of the centrifugal switch 56 are best seen in FIG- URES 3 and 4wherein the skillet 68 includes an annular cup-like cam surface 80.Extending'from the annular portion and integral therewith is asubstantially flat electrical contact portion 82. The flat portion hasapertures 84 and 86 formed therein through which the skillet supportpins and 72,;respectively, project in skillet retain.-

" ing relationship; Thepinmincludes a head p'ortion 88 j which aids" inretaining a spring tl in biasing relationship between the skilletflatfpo'rtion' 82'and the support pin head 88. "Support'p1n'72 is alsoformed'with a head .portion 21 to prevent the skillet 68 from-becomingdisto the nylon washer 132.

having a contact 116 at one end thereof, extending downwardly intoengagement with the offset control panel contact 76. Although members112 and 114 have been shown as separate parts, it is within the purviewof this invention to make these members as an integral member.

To provide means for changing main winding circuitry for the motor 16,the control board 66 carries main winding switch contacts 118, 120. Aflexible connection or pigtail 122 interconnects the skillet mainwinding contact 100 and control board contact'118. Similarly, a flexibleconnection or pigtail 124 interconnects skillet start winding contact168 and control board contact 120. For mounting the control board 66 toany suitable motor frame 126, apertures 128 are'mcluded thereon.

To actuate the skillet 68, weights 130 and a guide washer 132 of nylonor other suitable material, are mounted on a pin134 which is secured tothe motor shaft 136. The pin 134 is provided with a head 138 to hold thepin securely to the motor shaft 136. At the other end of the pin orrivet 134, a second head portion is formed to retain the assembly on thepin and particularly a weight return delay spring or bracket 142 'incorrect relationship A continuous return bias to the skillet actuatingwasher 132'is provided'by'a spring 133 interposed between the spring orbracket 142 and the washer 132. The nylon washer. 132 is adapted to rideon the annular cam surface as the motor 16 accelerates. As the weight136 and nylon guide washer 132 move out of engagement with the skillet68, the action of skillet spring is effective to pivot the skillet intoselective engagement with certain of the control board contacts, therebyto give the desired motor. control switching. a V 7 It should beapparent that, without further modification, the action of weight 136and nylon Washer 132 on the cam surface 80 of skillet 68 during motoroperation would be to energize or deenergize the motor. start winding 40at a particular rotational speed of motor shaft 136. However, thisinvention oontemplates'the control of a two-speed motor having a singlestart winding. It is conventional on a single speed motor to drop outthe start winding a-t ap-. proximately 75% of the running speed. Forexample; if

r a motors running speed is 1,725r'.p.n1., the start winding the motorspeed decreasing, the start windings would be 7 placed back in thecircuit by the action of the centnifiugally actuated switch 56 .atapproximately 1150 r.p.m. The

centrifugalswitch 56, it will be noted, has an inherentspeedwdiifterential of about 150 r.p.m. (1300 r.p.m. minus .1150 r.p.m.)This ;-is due to the changed center of gravity for weight and washer?132 asthey move from a position on the motor shaft 136 at standstill toa position at the outer terminus of pin 1 34at shaft running speed. But

where this controlcircuitry is to be'utilize'd in two-speed motoroperation and the low speed is below'the motor spced'at which the startwinding 'is'conveniently dropped out, it is apparent that certainmodifications are necessary to the centrifugally actuated switch portionof the motor control circuit if a single start winding is to be used forboth motor speeds. One of the basic requirements of this invention,therefore, is a wide differential, centrifugal switch. A highdifferential must be used on the start winding centrifugal control sothat the start winding cuts out at the cenventional point (1300 rpm.)for 1,725 high speed operation and resets at a speed (70 0 rpm. forinstance) below the 850 rpm. low speed operation. The centrifugal switch56, disclosed more particularly in the patent to Shewmon 2,623,979issued December 30, 1952, has been modified in a novel manner toaccommodate the novel motor control concepts of this invention.

, -A wide differential has been incorporated into the centrifugal switchthrough the application of a centrifugal weight returnfdelay springarrangement, shown generally at 142 (FIGURE 4). The spring 142 is formedin a U shape havinga top or base portion 144 and side portions orsections-146. Each side wall 146 is provided with a drawn out tab orprotuberance 148 which projects inwardly into the path of the skilletactuating washer 132. A teardrop configuration for the protuberances 148has been. found effective in promoting a smooth, flutterless movement ofthe washer 132 within the spring 142. Thus, as the'fwasher 132 movesradially outwardly in response to the centrifugal force imposed thereonby [the rotation of motorshaft 136, the spring protuberances 148 areforced smoothly outwardly to permit the washer 132 to pass. In thisregard, it should be apparent that the centrifugal force actingto movethe'weight 160 and washer 113-2 outwardly must be suificient to overcomethe radially inward bias of a spring 133 and the obstructing grippingaction of delay spring protuberances 148. Conversely, on thedeceleration of motor shaft 136, the actuating washer 132 will bereturned to the motor shaft when the bias of spring 133 is sufficienttoovercome the centrifugal force acting on the washer 132 and theresistance to return imposed by delay spring protuberances 14 8.

For purposes of clarity, schematic diagrams of the centrifugal skilletswitch 56 and i-tsnovel actuating elements are shown in FIGURES 5, 6, 7and 8 merely to illustrate the skillet positions relative to controlboard 66 and motor shaft 136. The wide differential producing delayspring 142 has been rotated 90 from its actual relationship in FIGURES 3and 4 to show clearly how the skillet provides the switching conceptsembodied in this invention. These relative positions will be discussedfully hereinafter in connection with the wiring circuitry for motor 16.However, briefly stated, these representations illustrate the followingrelationships. FIGURE 3 illustrates the motor 16 at rest or at theinstant of energizration. The skillet 68 is held to the lecfit againstthe 'bias of spring 90 by the action of nylon washer 132 against the topledge or surface 81 of the skillet 68. In FIGURE 5, the motor shaft 136has started to rotate (as indicated by the arrow) and the actuating disc1 32 started to move outwardly into sliding relationship to skillet camsurface 80. Skillet contact 116 has broken ctrcm control panel contact76, the start winding board contacts 102, 104 and skillet contacts 106,108 are made and main skillet contact 100 is still disengaged fromcontrol board contact 96. FIG- URE 6 shows the situation wherein boardcontact 76 and skillet con-tact 116 have moved apart to provide asuflicient gap at the point where contacts 96 and 100 mate to preventshortcircuit-ing during switching. Start winding contacts 102, 6 arestill in the circuit. FIGURE 7 illustrates the motor high speed runningcondition wherein the main win-dings are energized in parallel throughcontacts 96 and 100. The start winding is out of the circuit at brokencontacts 102, 106 and the skillet actuating disc 132 held fullyoutwardly against the action of spring 133 in accordance with thecentrifugal force imposed by rotating shaft 136. FIGURE 8 shows themotor situation when energized for low speed run with the main windingsconnected in series through contacts 96, 100. The centrifugal forceimposed upon the actuating disc 132 is in sufiicient in itself at motorlow speed to hold the disc 132 fully outwardly; therefore, therestraining action of teardrop protuberances =148 acts to prevent thereengagement of disc 132 and skillet cam surface during low speed run.This action effectively prevents the reenergization of the motor startwinding which would cause the motor to accelerate to a higher speed.

With reference to FIGURE 3, the skillet 68 is shown. In this regard, thenylon disc 132 is shown forcing the skillet 68 to the left pivotingabout contact 106 on 102 and 108 on 104. As the motor accelerates, theactuating disc 132 moves outwardly onto the skillet cam surface 80 in amanner to permit the skillet 68 to move to the right to permit contacts76, 116 to break before contacts 96, are made. The particular design ormodification of the skillet 68 over the prior teachings of Shewmon isdirected to preventing short circuits or arcing during any switchingoperation. Therefore, the idea is to secure as great a spread or breakas possible bebtween contacts 76 and 116 at the point where contacts 96and 100 are made (FIGURE 6). Considering the axial or rocking distancealong the skillet between contacts 98, 100 and 106, 108 and the paralleldistance between 106, 108 and .1-16, the longer the latter distance inrelation to the first distance, the greater will be the arc-preventingdistance between contacts 76 and 116 when skillet contacts 98, 100 meetboard contacts 94, 96. With reference to the actual skillet structure(FIGURES 3 and 4), these distances are incorporated by the addition of adepending arm 1114 which extends from skillet contact 98 to a pointadjacent control board contact 76.

As evidenced in FIGURE 9, the motor accelerates to approximately 75% ofhigh running speed for the motor 16 before the start windings are cutout. Thus, where low speed has been selected on dial 26 for switch 54,the motor 16 must coast or drift back to the low speed setting for themotor. FIGURE 7 illustrates that instant of start Winding cutout whereinthe centrifugal force imposed by the rotation of shaft 136 has forcedthe actuating disc 132 outwardly over the teardrop protuberances 148 andagainst the opposing bias of spring 133. As the motor shaft 136 slows inresponse to the low speed selection on speed selector switch 54, theactuating disc 132 will tend to return to its position adjacent themotor shaft 136. For instance, if the start winding cutout is atapproximately 75% of high speed run (1725 r.p.m.), the start windingwill cut out at approximately 1300 r.p.rn. Since the low speed operationis 850 r.p.m., the motor shaft 136 must drift from 1300 r.p.rn. to 850rpm. before the established circuitry effects a steady state low speedmotor operation. Should the start winding 40 be cut in during thisslow-down procedure, the motor 16 would again accelerate up to the startwinding cutout point of 1300 rpm. and an unwanted cycling would occur.This invention, however, provides means for preventing thereenergization of the start Winding 40 during low speed motor operation.With reference to FIGURE 8, the actuating disc 132 is shown resting onthe teardrop protuberances 148 during low speed operation. Spring 142,in this instance, has been designed to hold out the disc 132 against thebias of spring 133 as long as the motor shaft 136 is rotating atapproximately 700 rpm. or above. Thus, a wide differential has beenestablished wherein a single start Winding 40 is effective in either alow speed or a high speed situation. Of course, it should be obviousthat the resilience of spring 142 and the size of the protuberances 148may be varied to obtain any particular start winding cut-in desired.

Let us assume, now, that a high speed operation has been selected ondial 26 which places the switch 54 in position for high speed motoroperation. At the instant of energization, the relationship of thecentrifugally actuated switch 56 is in the position shown in FIGURE 3.As the motor accelerates in response to the high speed selection onspeed selector switch 54, the skillet 68 moves through the samepositions shown in FIGURES 3, 5, 6 and 7 and explained in. connectionwith the low speed motor operation. These positions are assumedsubstantially simultaneously and the start winding 40 is dropped out ofthe circuit when the rotational speed of motor shaft 136 reachesapproximately 75% of high speed running condition, i.e., approximatelyl300.r.p.m. At this point, the skillet actuating disc or washer 132 isthrown outwardly into the position of FIGURE 7 and the parallel wiredrelationship is established for main windings 36 and 38. Since highspeed has been selected on switch 54, the motor 16 will continue toaccelerate from the start winding cutout to the high speed operation of1725 rpm.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be' adopted.

What is claimed is as follows:

1. In a centrifugal device, a rotating member comprising a guide memberradially fixed to a rotatable shaft, a weight member slidably mounted onsaid guide member for radial displacement, an actuating washer attachedto said weight member, a U-shaped spring for delaying movement of saidwasher and a biasing spring circumscribing said guide member andinterposed between said delay spring and said washer, said delay'springhaving a base portion affixed to said guide member and a side portion inparallel relationship to said guide member and adjacent said washer, andsaid side portion having a teardrop protuberance thereon with a radiallyinner section and a radially outer section, said protuberance formedwith a small slope on the radially inner section for passing said washerupon acceleration of said shaft and a steep slope on the radially outer,section for restraining said washer upon deceleration of said shaft.

2. In a centrifugal device, rotating means comprising a rotatable shafta guide member fixed to said rotatable shaft and extending therefrom andan actuating member slidably mounted on'said guide member for guidedmove,

ment thereon in response to the rotation of said guide member, a springfor delaying movement of said actuating member and a resilient elementinterposed between said delay spring and'said actuating member, saiddelay spring connected to said guide member and having a side portion inparallel relationship to said guide member and adjacent said actuatingmember, and said side portion having a protuberance thereon with aninner section and an outer section, said protuberance formed with asmall slope on the inner section for passing said actuating member uponacceleration of said shaft and a greater slope on the outer section forrestraining said actuating member upon deceleration of said shaft.

3. In a centrifugal device, rotatable means comprising a rotatableshaft, a guide member fixed to said rotatable shaft and extendingtherefrom and an actuating member relatively movably mounted on saidguide member for guided movement thereon in response to the rotation ofsaid guide member, means for rotating said shaft and said guide member,said rotating means being controlled by said actuating member, yieldablemeans for delaying movement of said actuating member, said yieldablemeans connected for rotation with said guide member and having oneportion in spaced relationship to said guide member and adjacent saidactuating member, and said one portion having a protuberance thereonwith a radially inner section and a radially outer section, saidprotuberance formed with a small slope on the inner section for passingsaid actuating member upon acceleration of said shaft and a greaterslope on the outer section for restraining said actuating member upondeceleration of said shaft.

References Cited in the file of this patent UNITED STATES PATENTS V2,416,973 Wright Mar. 4, 1947 2,624,814 Shewmon Jan. 6, 1953 2,677,539Winslow May 4, 1954 2,897,309 Randol July '28, 1959 2,961,229 Parks Nov.22, 1 960 Cantonwine Apr. 24, 1 962

1. IN A CENTRIFUGAL DEVICE, A ROTATING MEMBER COMPRISING A GUIDE MEMBERRADIALLY FIXED TO A ROTATABLE SHAFT, A WEIGHT MEMBER SLIDABLY MOUNTED ONSAID GUIDE MEMBER FOR RADIAL DISPLACEMENT, AN ACTUATING WASHER ATTACHEDTO SAID WEIGHT MEMBER, A U-SHAPED SPRING FOR DELAYING MOVEMENT OF SAIDWASHER AND A BIASING SPRING CIRCUMSCRIBING SAID GUIDE MEMBER ANDINTERPOSED BETWEEN SAID DELAY SPRING AND SAID WASHER, SAID DELAY SPRINGHAVING A BASE PORTION AFFIXED TO SAID GUIDE MEMBER AND A SIDE PORTION INPARALLEL RELATIONSHIP TO SAID GUIDE MEMBER AND ADJACENT SAID WASHER, ANDSAID GUIDE MEMBER AND A SIDE DROP PROTUBERANCE THEREON WITH A RADIALLYINNER SECTION AND A RADIALLY OUTER SECTION, SAID PROTUBERANCE FORMEDWITH A SMALL SLOPE ON THE RADIALLY INNER SECTION FOR PASSING SAID WASHERUPON ACCELERATION OF SAID SHAFT AND A STEEP SLOPE ON THE RADIALLY OUTERSECTION FOR RESTRAINING SAID WASHER UPON DECELERATION OF SAID SHAFT.